Method and apparatus for applying coatings of molten thermoplastic material over closed pore elastomer foam substrates

ABSTRACT

In order to make weather seals from closed cell elastomer foam material, molten plastic is extruded over a substrate of the foam material. Surface reactions during extrusion are avoided by continuously pulling the substrate through an oven chamber to degas (and remove moisture from) the material at least on its outside to a limiting thickness of the order of 10-30 mil to form a skin or crust. The extrusion of the over-coating is carried out to form a sleeve while the substrate is still hot. Since the skin is a degassed region on the outside of the foam substrate, reactions which may cause blistering and prevent the extrusion of a smooth and firmly adhering skin are avoided. The substrate material is preferably a thermosetting EPDM rubber closed cell foam, and the over coating material is a thermoplastic elastomer (TPE).

[0001] The present invention relates to methods and apparatus forover-coating closed cell elastomeric foam material without engenderingreactions which may cause blistering or bubbling at the surface of thefoam during coating. The invention is especially suitable for use inmaking foam weather seals.

[0002] Weather seals have been made of closed-cell plastic foam materialwhich are over-coated to form a skin having a lower coefficient offriction than the foam material, see, for example, the followingpatents: Waskewicz, U.S. Pat. No. 4,238,260, issued Dec. 9, 1982;Yackiw, U.S. Pat. No. 4,328,273, issued May 4, 1982; Yardley, U.S. PatNo. 4,537,825, issued Aug. 27, 1985; Yackiw, U.S. Pat. No. 4,535,564,issued Aug. 29, 1985; Collinder, U.S. Pat. No. 4,538,380, issued Sep. 3,1985; Yackiw, U.S. Pat. No. 4,656,785, issued Apr. 14, 1987; andMertinooke, U.S. Pat. No. 5,192,586, issued Mar. 9, 1993.

[0003] It has been found that when the coating is over preformed plasticor thermoset elastomer foam material such as closed-cell EPDM rubber,reactions occur during extrusion which give rise to bubbles and pooradhesion of the coating. Such rubbers have been developed in the past,see, for example, Brenner, U.S. Pat. No. 4,181,780, issued Jan. 1, 1980,however, neither the problem caused by the extrusion of the moltenplastic for over-coating has not been either addressed or solved.

[0004] Accordingly, it is the principal object of the invention toprovide improved methods and apparatus for making weather sealsutilizing flexible strips (preferably cylinders or tubes) of closed-cellfoam material such as thermosetting EPDM.

[0005] It is a further object of the present invention to provideimproved methods and apparatus for over-coating a skin of plasticmaterial by extrusion thereof on a closed-cell foam substrate, which isoperative to raise the temperature of the substrate above a temperaturecritical to induce off-gassing of any materials or moisture in the poresthereby substantially eliminating the release of gas from the poresduring over-coating, which can affect the quality of the coating.

[0006] It is still a further object of the present invention to providean improved method of over-coating closed-cell foam materials whichenables such materials to be prefabricated and unwound from reels intoan extruder which carries out the over-coating process.

[0007] It is still a further object of the present invention to provideimproved methods and apparatus for over-coating foam material in theproduction of weather-stripping or other products using the foammaterial by pre-curing, pre-heating or out-gassing a surface layer ofthe foam while the foam is fed through an oven chamber through whichheated air is blown.

[0008] Briefly described, a weather seal made in accordance with theinvention has a flexible foam substrate which prior to the extrusion ofa skin of molten plastic material is heated to outgas at least a surfacelayer thereof. This layer is a crust which is essentially devoid ofcells from which gas can be released. Accordingly, during extrusion andover-coating, the foam substrate is essentially unreactive with the skinmaterial and the quality of the skin as regards to its adhesion to thesubstrate and smoothness is improved.

[0009] The forgoing and other objects features and advantages of theinvention, as well as a presently preferred embodiment of the apparatusfor carrying out the invention will become more apparent from a readingof the following description in connection with the accompanyingdrawings in which:

[0010]FIG. 1 is a block diagram schematically illustrating an embodimentof the invention;

[0011]FIG. 2 is a perspective view of the apparatus for driving andpreheating a closed-foam plastic elastomeric substrate prior toextrusion of a plastic over-coating thereon;

[0012]FIG. 3 is a fragmentary cross-sectional view of the closed-foamsubstrate after preheating and outgassing to form a crust or skin;

[0013]FIG. 4 is a front elevational view of the apparatus shown in FIG.2 taken from the right side;

[0014]FIG. 5 is a cross-section of the weather seal product as it iswound on the finished product reel for shipment to the customer; and

[0015]FIG. 6 is a side elevation of the apparatus shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Referring to FIG. 1, there is shown a first extruder 10 whichextrudes an attachment member 50 which is part of the finished weatherseal (see FIG. 5). The attachment member is illustrated as a T-shapedstrip 50 of plastic material, suitably polypropylene, which is insertedin a T-slot which holds the weather seal in a window frame or jam in amanner, as is conventional in fenestration applications. The attachmentstrip is cooled in a water bath 13 and is advanced along a path throughthe process by a puller 14, which may be provided by a pair of beltswhich engage the strip 50 on opposite sides thereof. The strip 50bypasses the process which is provided in accordance with a feature ofthis invention for handling the thermosetting foam elastomer 51, whichis the core or substrate to which the attachment strip 50 and the restof the material providing the weather seal is secured. The attachmentmember 50 proceeds to an extruder 17 which attaches the strip 50 to thefoam substrate and applies a coating 52 which is of a material thatprotects the foam and serves as a low-friction skin (the coefficient offriction of the skin 52 being less than the coefficient of friction ofthe foam substrate 51), as shown in FIG. 5.

[0017] The foam substrate 51 is prefabricated, and is in the form of acylindrical body, preferably a tube 51, as shown in FIG. 3. The tube iswound on a reel 15. The reel 15 is also shown in FIG. 4. The foamsubstrate 51 is preferably a thermosetting, elastomeric (rubber) foammaterial. A suitable foam is a closed-cell, non-oil resistant grade 2EPDM rubber. This material is defined by standard ASTM D-1056. It mayhave a compression load deflection of from 3 to 15 pounds per foot at50% of its outer diameter. It will be appreciated, of course, that thematerial used for the tube may be of different sizes. The size may varyfrom 50 mils to 600 mils in diameter (O.D.). The wall thickness of thetube may vary from approximately 25 mils to 300 mils. The cross-sectionof the substrate is preferably tubular, however, it may be a solidcylinder or have other cross-sectional shapes such as square, hexagonalor diamond shape, depending upon the application for the weather seal.The material of the coating 52, which is applied by the extruder 17 ispreferably a thermoplastic elastomer (TPE). It has been found that arubberized polypropylene is a suitable TPE material.

[0018] The foam substrate 51, is outgassed in an oven 16. This oven ispart of the apparatus shown in greater detail in FIGS. 2, 4 and 6. Theapparatus assures a sufficient dwell time in the oven and a sufficienttemperature to induce off-gassing in a surface layer or crust 54, asshown in FIG. 3. This crust may be approximately 10-30 mil thick.

[0019] While the invention is not limited to any theory for theformation of the crust, it is presently believed that the crust isformed as follows. Due to the heating to a critical temperature, sayapproximately 230° F., the foam core expands, that is its outer diameterincreases approximately 10% to 30% depending on the size and compositionof the foam and the process speed and temperature. In the process ofincreasing diameter, volatile gasses and moisture in the pores in anouter layer 54 of the foam are released. The remaining foam is withoutpores and therefore has a texture somewhat like the crust 54, as shownin FIG. 3.

[0020] Upon leaving the oven 16, the material cools slightly and may,for example, be about 200° F. upon reaching the extrusion dye 17 a ofthe extruder 17. The attachment strip 50 is combined and fed along theoutside of the foam substrate 51, reaching approximately to the outersurface of the substrate as shown in FIG. 5. Then, the TPE in moltenform is extruded to form the coating 52. The molten TPE may, forexample, be about 400° F. Because of the crust, and the elevatedtemperature of the foam substrate 51, there is provided a stable regionwhich is not reactive with the over-coating TPE material. Accordingly,there is no blistering or bubbling as would occur if the foam were notoutgassed prior to overcoating in the extruder 17. The coating 52obtained is therefore smooth and adheres completely to the substrate 51thereby providing a product of increased quality over that which wouldbe provided without the oven and outgassing process provided by theinvention.

[0021] The overcoated substrate 51, with the attachment strip 50 securedthereto by the overcoating 52, is then passed through a water bath 18and cooled, the cooled, totally solidified, weather seal is advanced bymeans of a puller mechanism 19 which may be similar to the puller 14.The weather seal is then fed over a dancer 56 and grabbed by a windingmechanism 20 which winds the weather seal product on a spool forshipment to the customer.

[0022] Referring to FIGS. 2, 4 and 6, the apparatus which provides theoven 16 is shown in greater detail. The oven itself, is a U-shaped,sheet-metal box. The metal may preferably be stainless steel towithstand the temperatures involved. The box in operation is closed by acover 58, which is not shown in FIG. 2 to illustrate the internals ofthe oven. The oven is open at the bottom and also at the top so that aplurality of turns of the substrate may be reeled through the oven.These turns are provided by pulleys 26 and 27 at opposite ends of theoven. These pulleys are driven positively by a drive mechanism includinga motor 31 which is connected to a drive pulley system including beltswithin guards 32 and 37. The belts are connected to the shaft of thepulley. In a typical embodiment, the length of the oven chamber 16 maybe six feet and there may be seven turns of the substrate foam aroundthe pulleys. The feed rate of the substrate may be sixty feet perminute. This rate may be kept constant and the temperature in the ovenchanged in order to accommodate different sizes of substrate, that isthe temperature may be higher for larger diameter substrate and lowerfor smaller diameter substrate.

[0023] The oven is heated by a forced air blower system. A pair ofcentrifugal blowers 24 a and 24 b are situated at the top of manifolds23 and 30. The manifolds are of a length corresponding to the length ofthe oven chamber 16. The manifolds are connected to the oven chamber bytubes 25 a and 25 b which are spaced from each other longitudinallyalong the sides of the oven chamber to provide a more or less uniformflow of air into the oven chamber. The tubes 25 a and 25 b may beelectrically heated by heater wire on the inside thereof. The controlsfor the drive motors and heaters may be in a box 22 which iselectrically connected to circuitry in enclosures 33 and 34. Themanifolds and the enclosures are mounted on a movable framework 28. Theframework is movable by virtue of lower legs thereof being mounted oncasters.

[0024] The substrate is supplied from a reel 15 which is mounted on ajournal having sufficient friction to provide back tension against theforce applied to the substrate by the pulley 26 and 27 and its motordrive 31. In the event that the substrate is fragile, the spool 15 maybe motor driven via a clutch which provides the necessary back tension.

[0025] Incoming substrate 51 is first wound around the lower pulley 27.The outgoing substrate after heating also leaves at the lower pulley 27.The substrate is then fed to a tensioner 21. A pair of rollers havingperipherys in contact but with grooves to permit the substrate 51 topass are located and the input and output sides 63 and 64 of thetensioner 21. The tensioner is therefore between the oven and theextruder as will be further apparent from FIG. 1.

[0026] The purpose of the tensioner is to minimize the force applied tothe substrate foam 51 by the puller 19. To this end, the tensioner has aweighted shuttle 68 which rides on wire guides 70. The shuttle has aroller 73 which contacts the substrate 51. As the tension increases, aloop of the substrate 51 between the side rollers 63 and 64 on oppositesides of the shuttle changes in size. When the tension increases, theshuttle moves upward, and when the tension decreases, the shuttleincreases the size of the loop. An ultrasonic sensor 75 measures thedistance between the shuttle and the face of the sensor. If the shuttleis above an upper limit, the sensor detects this condition and increasesthe speed of the motor 31 which drives the pulleys 26 and 27 so as toincrease the size of the loop. If the shuttle is below a lower limit,the sensor detects this condition and decreases the speed of the motor31 which drives the pulleys 26 and 27 so as to decrease the size of theloop. The tension of the foam substrate 51 is regulated by the weight ofthe shuttle which can be altered to handle very flimsy, small-diametersubstrate material as well as large diameter material.

[0027] From the foregoing description, it will be apparent that therehas been provided improved methods and apparatus for fabricating weatherseals of the type utilizing elastomeric (rubber) foam substrates whichare coated with a skin to provide the weather seal. Variations andmodifications in the herein described methods and apparatus willundoubtedly suggest themselves to those skilled in the art, such as theuse of open cell elastomeric foam substrates or the co-fabrication ofthe foam substrate during the fabrication of the weather seal.Accordingly, the foregoing description should be taken as illustrativeand not in a limiting sense.

1-16. (cancelled).
 17. Apparatus for precuring an outer layer of a bodyof thermosetting, closed-cell, foam elastomeric material adapted to be asubstrate for a foam weather seal, so as to accept a coating of moltenplastic without degassing during coating as can prevent application of asmooth, firmly adhering coating to said substrate, said apparatuscomprising a chamber having driven pulleys at opposite ends thereofaround which a plurality of turns of said substrate are wrapped andextend through said chamber, and means for flowing a stream of hot airthrough said chamber from at least one side thereof to at least one endthereof to establish temperature operative to precure said outer layer:18. The apparatus according to claim 17, wherein one of said pulleysreceives incoming substrate to said chamber and delivers substrateoutgoing from said chamber after being heated therein, and means fortensioning said substrate leaving said one pulley.
 19. The apparatusaccording to claim 18, wherein said tensioning means comprises aweighted vertically movable shuttle around which said outgoing substrateis guided to an extruder.
 20. The apparatus according to claim 17,further comprising a manifold, and air blower supplying air to saidmanifold, said manifold being disposed alongside said chamber, aplurality of heating tubes via which air is supplied to said chamberfrom said manifold and heated, said chamber being opened at at least oneend thereof, and said heating tubes being spaced longitudinally alongsaid chamber.
 21. The apparatus according to claim 17, furthercomprising a motor connected to said pulleys for simultaneously drivingsaid pulleys.